The relationship between various kinds of RNA and hemoglobin synthesis in the erythropoietic cells of the newt, Triturus cristatus, will be examined using biochemical methodology. Utilizing an erythropoietic system in anemic newts from which relatively homogeneous erythroid stages can be obtained, the amount of ribosomal RNA (rRNA) synthesized and accumulated in individual erythroid stages will be evaluated by means of radioactive labeling, sucrose density gradient centrifugation, and spectrophotometry. Messenger RNA directing hemoglobin synthesis will be identified by virtue of its specific stimulating capacity in Xenopus oocytes. Various aspects of presumed Hb mRNA species, including relative amounts synthesized in respective stages, will be examined relative to developmental stage and Hb synthesis. Polyadenylation of messenger RNA will be evaluated by various means including affinity chromatography and hybridization with labelled polyuridylic acid. Further characterization of the four newt hemoglobins will be performed utilizing chromatographic and electrophoretic methods. By means of radioactive labelling and absorbance, the rate and amount of hemoglobin synthesis and of other erythroid cell proteins will be measured in various erythroid stages. Quantitative relationships between the various RNA forms and hemoglobin synthesis will be analyzed in an effort to evaluate nature and extent of controls operable in RBC development.